A standard gas-fired heat gun of the type used for shrink wrapping comprises an elongated housing having an upstream end provided with a gas nozzle that projects a stream of combustible gas axially along the housing. A mixing tube concentric with the gas stream has a large-diameter upstream end spacedly surrounding the nozzle and and a small-diameter downstream end opening into a combustion chamber. Thus as in a jet pump the stream of gas sucks air into the upstream end of the tube and mixes with it. An igniter in the combustion chamber ignites the mixture. Such a heat gun can be used to shrink a foil wrapped around goods to package them.
In order to ensure adequate mixing of the oxygen-containing combustion-supporting air and the combustible gas. It is normally necessary to provide a relatively long mixing tube. As a result the gun has a relatively large overall length that makes using it fairly difficult.